B. B. Biochem. 64, 2121-2127 (2000).

Nishiyama, K., Suzuki, H., and Tokuda, H.

SecE is an essential component of the protein translocation machinery of Escherichia coli and has three transmembrane stretches. An N-terminal region (SecE-N) encompassing the first two transmembrane stretches is dispensable for protein translocation but a SecE derivative (SecE-C) lacking this region is very unstable. We show here that FtsH, the AAA (ATPases associated with diverse cellular activities) family protease, causes the instability of SecE-C. SecE-C became stable when SecE-N was co-expressed. Deletion of the N-terminal region of SecE also rendered the SecE-SecY-SecG complex unstable. In spite of these alterations, the N-terminal region of SecE had little stimulatory effect on protein translocation in vivo or in vitro.